Sound communication system



Dec. 15, 1936.

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DETECTOR bt? @Homey Patented Dec. 1936 UNITED STATESy 2.063.946 soUNn conmUmcA'rIoN SYSTEM George wasninmuriem, cambridge, um;

Application February 9, 1932, Serial No. 591,889

1s claims. (ci. 179-1) The present invention relates to the transmission 'and reception of intelligence, using sound vibrations as the-agency of communication, and more particularly to communication by sound along i solid-vibration conductors, like wires.

From a more limited aspect, the invention relates i sound in themetal to the other end; and to convert or reconvert the mechanical vibrations at the said other end or some other point into electrical energy, which may be put to any desired use.

Other objects will be explained hereinafter and will be particularly pointed out in the appended claims. v

With these ends in view, a feature of the invention resides in mechanically transmitting a l sound beam over a linearly disposed, solid conductor of longitudinal vibrations to a receiving device o and converting therein the' energy of the sound beam into electrical energy. According to a preferred embodiment of the invention, a sound beam of a supersonic frequency is produced electrically or otherwise, and is modulated by the sonic frequencies of the sound matter to be transmitted. The beam thus modulated is then propagated along a linearly disposed medium. such as a wire, and is demodulated and converted into electric vibrations at the receiving station. Ii. deo sired, of course, these electric vibrations can be reconverted into acoustical waves' and thus made audible.

The invention will be explained in greater detail in connection with the accompanying drawings.

5 in which Fig. 1 is a diagrammatic view of apparatus and circuits constructed and arranged for transmission and reception purposes according to one embodiment of the present invention; and Figs. 2 to 12 are diagrammatic views of modii- D cations.

The vibrations may be excited at one end of the wire b y magnetostriction (Fig. l) electrostatically (Fig. 2), by aymagnet-and-diaphragm combination (Fig. 3), by an incident sound wave (Fig. 4)

3 by a sound wave applied mechanically (Fig. 5)',

or by any other means. The vibrations received at the other extremity of the wire may be transformed into electrical energy by magnetostriction (Fig. 1), a resistance-changing device, such as a carbon-granule microphone 9 (Flg'. 6), a piezo- 5. electric crystal 1 (Fig. 7), an electromagnet-anddiaphragm 8 (Fig. 8), or by other methods.

Referring, first, to the right-hand, transmitting end of Fig. l, a wire core 2, preferably of nickel, nickel-steel, nickel-copper, nickel-cobalt, chrome- 10 nickel, chrome steel, or of any other metal element or alloy, characterized by comparatively large magnetostrictive effects, is shown positioned substantially in axial alinement with, and driven by, one or more inductive field solenoid coils i0. A plurality of series-connected coils I0 are illustrated in Fig. l as mounted over the core 2, for reasons which will be-explained hereinafter. 'I'he coils i0 are provided with conductors or leads I and 3, by means of which they are connected in 29 the output circuit, between the lament or cathode 26 and the plate or anode 28, of an oscillator 30, which serves as a source of high-frequency electric oscillations for producing the mechanical vibration in the wire 2. The oscillator 30 is illus- 25 trated as of the type having a vacuum-tube, or electric-discharge device, but it may be of other types than that shown such, for example, as are illustrated and described in Letters Patent l,'150,1'2 4,'issued March 11, 1930. If the driving so coils It do not carry direct current normally in the circuit, it will be well to add a battery to supply it for purposes of magnetic polarization, as is done, for example,- at 3l i in the receiving station of the same figure. Plate modulation may be 35 employed, as illustrated, a microphone 10 being coupled through a transformer 66 to an amplifier 61 which, in turn, is coupled to the plate circuit of the tube30 by a modulation transformer 68.

I! grid modulation, however, is desired, the input circuit of the oscillator 30, between the filament 26 and the grid or control electrode 21. may be coupled by-a modulation transformer (not shown) to the microphone. A.

The wire core 2 is `connected by a wire I 45 of any suitable sound-vibration-carrying material, such as iron, phosphor .bronze or copper. to

a magnetostrictive core 5 at the take-0E device,

as illustrated at the left-hand, or receiving, end

of Fig.l 1. The core 5 is provided with coils 6, 50

corresponding to the coils I0 for the core 2. If

desired, of course, the wire l may be of the same metal as the cores 2 and 5, but a good con- -struction is a cheaper wire l, with nickel tubes 9i' Wires 2 and 5 soldered at its ends. A beam 55 of high-frequency sound, modulated by speech in the microphone 16, is thus directed from the sending to the receiving end along the wire 4, and is demodulated at the receiving end. In place of microphone modulation, a key lill may beused to interrupt the oscillator current so as to send telegraphic code. Mechanically to transy mit telephonie or telegraphic signals over a linearly disposed, sound conductor by means of a supersonic'carrying wave in this mannerI is believed to be a newachievement.

The coils 6 are shown in Fig. 1 as series-connected, in circuit with a high-.frequency transis shown connected to three stages of amplificav tion, represented by the tubes 14, 32, and 34, and to a detector 36. The output circuit of the detector tube 36 may contain a telephone receiver 44 or may connect to the input leads of an audio amplifier 69. Fewer or more stages of amplification may be used. A negative bias for the input circuit of the tube 14 is illustrated by the battery 50.

In the system of Fig. 2, the vibrations in the wire` 4 are set up by a condenser transmitter 1l, the plates of which vibrate in synchronism with the applied electromotive force, the electric energy therefor being supplied through a transformer 18-from any source of alternating current 16. In Fig. 3, the vibrations are produced by electromagnetic action.' 'The battery 311 of the oscillator shown in Fig. 3 may be omitted if the core 19 of the electromagnet is permanently magnetized. j

The modulated high-frequency sound, instead of traveling over the wire 4, may be caused to travel through theair. It is not necessary, furthermore, that the sound beam should be transmitted completely by wire from the sending end to the` receiving end. The wire conductor mair be interrupted so thatthe sound waves have to travel partly through th`e air between the sending and receiving stations.

In Fig. 4, the 'vibrations in the wire 4 are shown as excited by the impinging of an incident soundwave, representedby the arrow 18, on a diaphragm 80, of any desired character, mechanically connected to the wire 4 that leads to the receiver wire 5. This illustrates diagrammatically one of the most important applications of the invention. By the use of this invention, any sound-detecting apparatus whatsoever which is set into vibration by a sound wave incident upon it may be made to excite vibrations in one or more wires leading from the device to apparatus located elsewhere, which will convert the vibrational energy communicated to it by the wire or wires into electrical energy. For example, if a watch 8l is hung on one end of the wire 4, as illustrated in Fig. 5, the superaudible components of the ticks of the watch at, say, 20,000 cycles per second, will be sent large distances tothe other end of the wire and picked up at the receiving end.

The possibility of thus separating the vibrating member from the electrical apparatus solves. among others, problems of insulation when the vibrating member is immersed in water or other conducting medium, for the electrical apparatus can now be entirely outside the medium, and located at any convenient point.

Other advantages accruing from the use of this invention are even more important. Instead of using one wire, a number of wires maybe used for transforming the vibrational energy, which will thus be transformed into electrical energy more eiilciently. For instance, for directive discrimination in favor of an incident sound beam coming in the direction of the arrow 83, a plate diaphragm 82 (Fig. 9) may beused, disposed at an angle 0 with the wave-front line at right angles to the direction of the beam, vibrating in segments as a standing-wave system, as decribed in application Serial No. 591,838, filed of even date herewith. As is also described in the said application, if Vo is the velocity of sound in the medium, such as air or water, and V is the velocity of propagation of elastic waves in the material of the diaphragm 82, then sin 9=%- a plurality of take-on wires 84 may be aflixed at l properly spaced points, instead of having a single take-off element, and the sound Waves thus produced may be conducted along all these wires to a common converter 86 of sound into electric energy. The transforming apparatus is shown in Fig. 9 as magnetostrictive.

Again, with the possibility of multiple takeoff, a plate receiver may be constructed which will receive or transmit sound along one direction only, namely, the normal to the plate. All that is necessary is to construct a plate in which the velocity of propagation of transverse vibration is very low, or one in which tranverse vibrations are rapidly damped out. This may be done by constructing the diaphragm of very thin metal or of some substance in which the damping of vibrations is high, such as rubber. If desired, each wire may be terminated in a small metallic diaphragm 88, and the whole number of these diaphragms supported in a plane array by a common rubber diaphragm or lnany other suitable way, as illustrated in Fig. 10. Under these conditions, each wire 84 will pick up and transmit vibrations from the incident sound independently, but if the various receiving elements are not situated in the same region (or similar regions) of pressure of the incident wave, the various impulses at the transformation apparatus will not, if the wires be of the same length, be in the same phase, and the net signal will be less than if all the separate impulse be made to add in phase. Signals arriving in any oblique direction, as indicated by the arrow 83, will give less effect than those arriving in the normal direction, indicated by the arrow 3| 2.

The wires 84 are shown in plane view only, so that they appear to be of diierent lengths. Actually, of course, they must be of equal lengths if the receiving diaphragm of Fig. 9, or the array of receiving units |88 of Fig. 10, lie in a plane.

If it is desired to locate the direction of a sound source without rotating the vibratory member 82 or 88, 90, it is possible to do so by altering the lengths of the sound paths from the device to the transformation apparatus to compensate for the difference in phase at the vibrator. This may be done in a number of ways. of which one 75 acess-1c isshown in Fig. 11. Any system like this oi compensation for phase requires that there be eifectively no standing waves at the point where the take-oit coils are located. for in a standingwave system, the nodes and loops are xed in space. Inorder to get rid of standing waves, the wave reected from the end of the wire must be eliminated in some way. This may be done by making the free ends 92 of the wires of magnetostrictive material long, so that any wave which passes the coil travels a long path before returning to the coil, by reection, and is thereby diminished by the natural attenuation along the wire. This attenuation may be increased by wrapping the wire tightly in some damping substance such as rubber or felt, and the necessary ireelength thus reduced.' Coils 84 are shown in Fig. 11 mounted on a. rotatable arm 96 equipped 'with a pointer 98.

Y If it is desired to utilize a wire as a means of communication of Y intelligence between two points, the wire can be set into vibration at the transmitter by the methods illustrated in Figs. 1 to 3. This yvibration may conveniently be of a super-audible frequency and may be made to carry any modulation desired by methods well known in the art. It is obvious that a single wire may thus be made to conduct a number oi mes-A sages at once by exciting' it with a number of high frequencies, each modulated as desired. and equipping its receiving end with a number of takeoi devices, each tuned to one of the transmitted carrier frequencies.

It is possible thus to utilize high-voltage transmission lines IBO forthe transmission of speech. Sound vibrations may be communicated to the wires through a rod I 02 of glass or other insulating material, and taken from the wire at the receiving end by the same method above described as illustrated `in Fig. 12, where an os- ,cillaton which may be modulated, is indicated at IM, and an amplifier and detector at |06.

The separation of the vibrating member from the electrical apparatus, which .latter may be located at any convenient point, makes it possible to utilize this invention as a. link for communicating between points where the laying of a telephone line would be difcult or expensive, as for -instance, across a water channel or other con ducting medium. Inasmuch as the method of transmission is not electrical, and as the electrical apparatus is entirely outside the water or other conducting medium, no insulation is 'rek quired on the wire. Thus a single, bare wire, laid across a water channel, may replace a carefully and expensively insulated telephone cable.

The invention has kalso other uses, such aspicking up sound from approaching trains on tracks.

If a number of coils I0 or 6 for the magnetostrictive core are employed, instead of only one, spaced along the core one wave-length apart, magnetostrictive excitation will be produced as if the coils were hunched at one spot, but without obiectionable'heating effects or over-magnetization. v A single coil i0 or'6 will, however, as before stated, operate.

As illustrated in Fig. 12, it is well to enclose the coil or coils` about the magnetostrictive core, particularly at the receiving stations, in a shield .or shields I I2, so as to prevent stray electromagnetic waves from interfering with the reception. `'I'he sound waves will, however, be admitted into the shield overthe sound conductor to the core. The shield may have an opening H3. for the eri--v trance ofthe sound conductor, or thesound conductor may be integrally connected with the shield H2. In this latter case, the shield should be constructed of magnetostrictive material so as to function as a magnetostrictive external core for the coil H2 according to the invention disclosed in copending application. Serial No. 592,320, illed February ll, 1932, and the inner core 5 may be omitted.

It will be understood that the invention is not restricted to the exact embodiments thereof that are illustrated and described herein, as modifications may be made by persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention, as dened in the appended claims.

What is claimed is:

1. Apparatus of the characterrdescribed comprising a coil, a vibratory, magnetostrictive core magnetostrictively associated with the coil, and a.

-linearly disposed, solid conductor of longitudinal,

mechanical vibrations directly connected with the core and extending over a considerable distance, whereby mechanical vibrations magnetostrictively produced in the core through the action of the electric energy of an electric current in the coil will be mechanically transmitted from the core to the conductor, or whereby mechanical vibrations in the conductor will be transmitted to the core in order magnetostrictlvely to convert the mechanical energy of the said mechanical vibrations into electric energy of an electric current in the coil.

2. Apparatus of the character described comprising a mechanically vibratory core, a linearly disposed, solid Y,conductor of longitudinal, mechanical vibrations directly connected with the core and extending over a considerable distance, and means for electrically producing mechanical vibrations in the core or responsive to mechanical vibrations in the core to convert the mechanical energy of the mechanical vibrations of the core into electric energy, whereby mechanical vibrations produced by the said means in the core will be mechanically transmitted from the core to the conductor, or whereby mechanical vibrations in the conductor will be transmitted to the core inV order to convert the mechanical energy of the said mechanical vibrations into electric energy.

3. Apparatus of the character described comprising a coil. a. vibratory, magnetostrictive core magnetostrictively associated with the coil, a linearly disposed, solid conductor oi' longitudinal, mechanical vibrations directly connected with the core and extending over a considerable distance, whereby mechanical vibrations in the conductor will be transmitted to the core in order magnetostrictively to convert the mechanical energy of the said mechanical vibrations into the electric energy of an electric current in the coil, and means for utilizing the said electric energy to produce intelligible indications.

4. A method of communication that comprises producing a sound beam of superaudible frequency by means of an electric current of superaudlble frequency, modulating the electric current at a. lower frequency, transmitting the resulting sound beam, receiving the transmitted sound beam, converting thev mechanical energy of the received sound beam into electric energy of an electric current, demodulating the lastnamcd electric current, and converting the elecinto intelligible indications.

5. Apparatus 4of the character described comprising a coil, a vibratory; magnetostrictive core. magnetostrictively associated with the coil, a linearly disposed, solid conductor of longitudinal mechanical vibrations directly connected with the core and extending over a considerable distance, and means for modulating the electric current inthe coil, whereby mechanical vibrations magnetostrictively produced in the core through the action of the electric energy of the y modulated electric current in the coil will be Asuperaudible frequency in the coil, and means for modulating the electric current in the coil at a lower frequency, whereby mechanical vibrations magnetostrictively` produced in the coil through the action of the electric energy of the modulated electric current in the coil will be mechanically transmitted from the core to theconductor.`

' 7. Apparatus ,for -the directive discrimination of a sound beam in a medium comprising a vibratory diaphragmdisposed in the medium, a coil', a vibratory, magnetostrictive core magnetostrictively associated with the coil, and a linearly disposed, solid conductor 4of longitudinal, me-

chanical vibrations directly connected with the core and the diaphragm, whereby mechanical vibrations magnetostrictively produced in the core through the action of electric energy of an electric current in the coil will be mechanically transmitted from the core to the conductor and from the conductor to the' diaphragm, or whereby mechanical vibrations in the diaphragm will be transmitted from the diaphragm to the conductor and from the conductor to the core in order magnetostrictively to convert the mechanical energy-of the said mechanical vibrations in `the diaphragm intoelectric energy of an electric current -in the coil.

8. A method of communication that comprises producing a sound beam by means of an electric current, modulating the electric current, transmitting the resulting sound beam over a linearly disposed sound conductor, receiving the transmitted sound beam, converting the mechanical energy o! the received sound beam into electric energy of an electric current, demodulating the last-named electric current, and converting the electric energy of. the demodulated electric current into intelligible indications.

9. A method of communication that comprises producing a sound beam of superaudible frequency by means of an electric current of superaudible frequency, modulating the electric current at a lower frequency, transmitting the resulting sound beam over a linearly disposed sound conductor, receiving the transmitted sound beam, converting the mechanical energy of the received sound beam into electric energy of an electric current, demodulating the last-named electric current, and converting the electrical energy of the demodulated electric current into intelligible indications.

10. Apparatus of the character described comprising a plurality of coils, a vibratory, magnetostrictive core magnetostrictively associated with the coils, and means connecting the coils with an alternating-.current circuit, the coils being spaced from each ,other at distances such that the magnetostrictive interaction between the core and an electric current in the coils i's cumulative.

11. In a communication system, a link for connecting two points of the system comprising a mechanically vibratory member at each of the points, Aa linearly disposed, solid conductor of longitudinal, mechanical vibrations directly connected with the members, means for electrically producing mechanical vibrations in one of the members, whereby thelmechanical vibrations will be transmitted over the conductor to the other member,l and means responsive to the mechanical vibrations in the said other member to convert the mechanical energy of the said mechanical vibrations into electric energy.

12. A method of communication that comprises producing a sound beam of carrier frequency by means of an electric current of carrier frequency, modulating. the electric current at a lower frequency, transmitting the resulting sound beam, receiving the transmitted lsound beam, converting the mechanical energy of the received sound beam into electric energy of an electric current, demodulating the last-named electric current, and converting the electric energy of the demodulated electric current into intelligible indications.'

13. A method o! communication that comprises producing a sound beam of carrier frequency,` causing the intensity of the sound beam to `va'ry in direct correspondence to predetermined modulating frequencies, transmitting the resulting sound beam, receiving the transmitted sound beam, and converting the intensity variations of the sound beam at the said modulating frequencies into intelligible indications.

GEORGE W. PIERCE. 

